The proposed project is a comparative study of mammalian hearing with emphasis on sound localization. The long-range goals are to determine the ecological, morphological, and physiological correlates of the variation in hearing and sound localization abilities of mammals. The immediate aim is to examine the auditory abilities of species selected because a knowledge of their abilities would help answer questions concerning the evolutionary, anatomical, and physiological bases of hearing. The immediate goals of this project are to a) determine the hearing abilities of three species of fossorial rodents (mountain beaver, naked mole rat, and prairie dog), b) investigate the relationship between sound localization acuity and vision, c) compare the ability of mammals with mobile and nonmobile pinnae in localizing sounds in the lateral fields. d) investigate the relation between sound localization and brainstem morphology by performing preliminary histological analyses of the superior olivary complex of species whose localization ability has been determined, e) investigate the effect of albinism on binaural functions by determining the auditory abilities of albino cats, and f) determining the hearing and/or sound localization abilities of two species of interest to auditory research: the spiny mouse and chinchilla. The ultimate goal of this project is to gain information which would he of use in understanding the function of the human central auditory system. Of immediate relevance to human health is the proposed study of albino cats which is expected to provide information concerning the consequences of albinism to hearing.